6H2O System Research Articles

1,2,4-Triazolyl-4-acetate: a ditopic ligand combining soft and hard donor sites in homometallic (AgI) and heterometallic (AgI/UVI) coordination polymers

A 1,2,4-triazol-4-yl-acetic acid (trGly-H) was used for the synthesis of AgI and AgI/UVI coordination polymers. The composition space diagram was built for the AgNO3/trGly-H/UO2(NO3)2·6H2O system shows the crystallization fields of two AgI/UVI-compounds were found.

Study of ion dynamics of LiI·6H2O in the supercooled liquid state using NMR spectroscopy and ionic conductivity measurements

Ion dynamics in the liquid and supercooled liquid state of LiI·6H2O were studied by nuclear magnetic resonance (NMR) spectroscopy and ionic conductivity measurements. The self-diffusion coefficients of the water molecules and lithium ions were measured by 1H and 7Li pulsed gradient spin echo NMR (PGSE-NMR). The temperature dependences of the DC ionic conductivity and diffusion coefficients of lithium ions and water molecules were well-fitted by the Vogel-Tamman-Fulcher (VTF) law, similar to those of the LiCl·RH2O system. The conductivity and lithium diffusion coefficients of the LiI·6H2O system were more than twice those of LiCl·7H2O in the supercooled liquid state below 200 K, which could be attributed to the larger size of the iodide anions than that of chloride anions. The temperature dependence of the correlation times calculated from NMR T1 relaxation deviated from the VTF law at low temperatures because of the local orientational fluctuation of the water molecules.

Hydration study of MgSO4 using different theoretical and model approaches. ¿is there a proton transfer?

A controversy about a proton transfer (PT) from a water molecule to the sulfate ion is presented in theoretical studies of isolated MgSO4·6H2O systems in the forms of contact (CIP) and solvent-share (SIP) ion pairs. Calculations with different methods and basis sets were performed without and with solvation. The results show that a PT may occur in a system without solvation; however, the no proton transfer (NPT) structure is also stable. The formation of either PT or NPT depends on the starting location and orientation of the sixth water molecule. In particular, we find that solvation favors NPT formation.

Solubility of the Metal Precursor Ni(NO3)2·6H2O in High-Pressure CO2 + Ethanol Mixtures

The solubility of Ni(NO3)2·6H2O in high-pressure CO2 + ethanol mixtures was measured using a high-pressure variable-volume view cell from (308.2 to 353.2 K) and up to 25.0 MPa. This compound has been used previously as a Ni precursor in metal deposition experiments using supercritical CO2. Ni(NO3)2·6H2O was not soluble in pure CO2 but the addition of ethanol into the system allowed the solubilization of the hydrated salt in the mixture. Mole fraction of Ni(NO3)2·6H2O varied from 1.67 × 10–4 to 1.97 × 10–3. At these salt concentrations, the phase diagram of the CO2 + EtOH + Ni(NO3)2·6H2O system resembled that of the CO2 + EtOH binary system and, at the studied conditions, a vapor–liquid equilibrium was observed. For the higher ethanol concentrations, the bubble points closely matched those of the CO2 + EtOH system. For the lower EtOH concentrations, however, much higher solubilization pressures were required, due to the release of water molecules from the salt into the solution. Ni(NO3)2·6H2O solutions wer...

Possible Formation of H3O+ Cations Due to Aluminum Fluoride Interactions with Water.

The isomeric structures formed by the aluminum fluoride (AlF3) system and surrounding water molecules were theoretically examined by employing MP2 and CCSD(T) methods and the aug-cc-pVDZ basis set together with the polarized continuum solvation model within a self-consistent reaction field treatment. The calculations performed for the AlF3·n(H2O) systems (n = 1-6) revealed that facial and meridional octahedral structures correspond to the lowest energy isomers for the AlF3·4H2O, AlF3·5H2O, and AlF3·6H2O systems, whereas the isomers containing the H3O+ and AlF3OH- fragments were predicted to be less stable by only 5-7 kcal/mol, which indicates the possible formation of the hydronium cations in such systems even at room temperature.

A green approach for arylation of phenols using iron catalysis in water under aerobic conditions

The first efficient iron-catalyzed coupling of aryl iodides with phenols was developed exclusively with water as solvent. The reaction is performed with low cost and readily available FeCl3·6H2O and DMEDA catalytic system providing diaryl ethers in good to excellent yields. The effectiveness of this reaction was further revealed by compatibility with a wide range of functional groups. Moreover, the procedure is rendered simple as this transformation is carried out in the presence of air. Thus, the protocol represents a facile, economical and eco-friendly procedure to access diaryl ethers.

Host-guest structural architectures in hydrous alkaline (Li, K) uranyl chromates and dichromates

Two new (Cr2O7)2− and/or (CrO4)2− containing uranyl compounds with K and Li: [K10(Cr2O7)2(H2O)2]|(UO2)(CrO4)4| (1) and |Li2(H2O)5|[(UO2)(CrO4)2] (2) were obtained via two various synthesis routes in the K2Cr2O7–CrO3–(UO2)(NO3)2·6H2O–H2O (1) and LiCl–CrO3–(UO2)(NO3)2·6H2O (2) systems. The key feature of the crystal structure of 1 is the formation of hydrous potassium dichromate [K10(Cr2O7)2(H2O)2]6+ 2D units acting as hosts for guest |(UO2)(CrO4)4|6− clusters. (Cr2O7)2− groups are not bonded via common oxygen atoms to (UO2)2+ in 1 which is the first example of such structural architecture in uranyl oxysalts with tetrahedral TO4 (T=Si4+, As5+, P5+, Cr6+, etc.) anions. In the structure of 2, UrO5 and CrO4 coordination polyhedra share corners to produce [(UO2)(CrO4)2]2− layers with |Li2(H2O)5|2+ tetramers guest species in the interlayer.

Catalytic conversion of cellulose into 5-hydroxymethylfurfural over chromium trichloride in ionic liquid

An efficient method for converting cellulose into 5-hydroxymethylfurfural (5-HMF) using an inexpensive ionic liquid tetrabutylammonium chloride (TBAC) and relatively low-toxicity catalyst of chromium (III) trichloride (CrCl3·6H2O) was developed. The effects of hydrochloric acid loading, catalyst dosage, reaction temperature and time on the yield of 5-HMF were surveyed to achieve optimal reaction conditions. A 5-HMF yield of 43.7% was obtained within 90 min at 140 °C using oil-bath heating. Glucose and starch were also investigated as feedstock to produce 5-HMF in TBAC/CrCl3·6H2O system, in which the 5-HMF yield was considerable. After 5-HMF was extracted, TBAC/CrCl3·6H2O could be used for several runs.

Efficient Conversion of Glucose into 5-Hydroxymethylfurfural by Chromium(III) Chloride in Inexpensive Ionic Liquid

An efficient process was developed for the conversion of glucose into 5-hydroxymethylfurfural (HMF) in the relatively low-toxicity and inexpensive catalytic system of chromium(III) chloride (CrCl3·6H2O) catalyst and tetraethylammonium chloride (TEAC) ionic liquid. An HMF yield of 71.3% was achieved at 130 °C for only 10 min under conventional oil-bath heating. The TEAC/CrCl3·6H2O system was found to be tolerant to high water content and high glucose concentration and could be recycled, exhibiting stable activity after five successive runs. Moreover, satisfactory results were achieved when fructose, sucrose, and cellobiose were used as feedstocks. This work might also provide useful information for the production of HMF from biomass.

Formation of solution inclusions in bicrystals of potassium-cobalt/potassium-nickel and ammonium-cobalt/ammonium-nickel sulfates

The crystallization of epitaxial layers from aqueous solutions in the K2Co(SO4)2 · 6H2O-K2Ni(SO4)2· 6H2O and (NH4)2Co(SO4)2· 6H2O-(NH4)2Ni(SO4)2 · 6H2O systems has been studied. A mechanism is proposed to explain the experimentally observed phenomena, taking into account the effect that elastic stresses have on the crystallization kinetics.

A study of the mechanisms of defect formation in K2Ni(SO4)2 · 6H2O/K2Co(SO4)2 · 6H2O bicrystals grown from aqueous solutions

The K2Co(SO4)2 · 6H2O-K2Ni(SO4)2 · 6H2O system has been studied, and a series of K2Ni(SO4)2 · 6H2O/K2Co(SO4)2 · 6H2O bicrystals have been grown. The processes of defect formation at the substrate/layer interface K2Co(SO4)2 · 6H2O/K2Ni(SO4)2 · 6H2O are studied by probe microanalysis, X-ray topography, and optical microscopy. It is found that inclusions and threading dislocations are formed at the interface, due to which elastic stresses relax in the crystal. Nickel is nonuniformly distributed in the layer; its concentration decreases with an increase in the layer thickness, which is indicative of substrate dissolution in the initial stage of interaction. A way for the elastic mismatch stresses to relax in heterostructures of brittle crystals obtained from solutions at low temperatures is proposed which implies the formation of inclusions at the substrate/layer interface.

Three coordination polymers with helical chains based on methylenediisophthalic acid (H4MDIP)

Based on methylenediisophthalic acid (H4MDIP), three novel coordination polymers {[Mn2(MDIP)(bime)(H2O)2]2·2H2O}n (1) [bime = 1,2-ethanediylbis(imidazole)], {[Mn3(HMDIP)2(H2O)4]·4,4′-bipy·3H2O}n (2) [4,4′-bipy = 4,4′-bipyridine], and {[Co5(MDIP)2(H2O)6(μ-OH)2]·7H2O}n (3) have been synthesized and characterized by IR spectra, single-crystal X-ray diffraction analyses and thermal stability studies. The introduction of the bime and 4,4′-bipy ligands into Mn(CH3COO)2·4H2O and H4MDIP system leads to the formation of complexes 1 and 2, and the absence of the second ligand in the Co(NO3)2·6H2O and H4MDIP system leads to shape complex 3. Complex 1 is a 3D architecture with [Mn(–OCO–)]∞ helical chain. Coordination polymer2 is a 2D sheet structure with trinuclear unit, in which two kinds of 21 helical chains ([Mn(IP)]∞ (IP = isophthalic acid) and [Mn(MDIP)]∞) are included. Complex 3 exhibits the 3D porous structure with a pentanuclear cobalt unit in which a 1D shallow helical chain of hydrogen-bonded water molecules is shaped. From the topology point of view, complex 1 exhibits a (4,6)-connected network with the Schläfli symbol (42.63.8)2(44.62.74.84.9), complex 2 displays a (3,6)-connected network with CdI2 topology, and complex 3 displays a (4, 8)-connected network with Schläfli symbol (44.62)2(416.612) which is a decorated scu net.

Modeling gas hydrate equilibria in electrolyte solutions

Virtually all gas hydrate models use a statistical thermodynamic approach to describe solid phase gas hydrates. An alternative to this model is a “solid solution” model based on classical thermodynamics. Various models are used to describe associated gas phase and aqueous electrolyte properties. None of the electrolyte models, however, are state-of-the-art with respect to gas/electrolyte interactions. The objectives of this work were to (1) develop a classical thermodynamic approach for gas hydrate equilibria, (2) incorporate these hydrate chemistries into a state-of-the-art electrolyte model, and (3) validate the gas hydrate/electrolyte model. The model used the Pitzer approach to estimate as functions of temperature and pressure: (1) activity coefficients for cations, anions, and soluble gases, and (2) the activity of water. This model explicitly considers interactions between soluble gases and electrolytes. The Duan model was used to characterize the gas phase. Solubility products were calculated for CH 4⋅6H 2O ( T = 180 – 298 K ) and CO 2⋅6H 2O ( T = 180 – 283 K ) . A “solid solution” model was used to define mixed CH 4–CO 2 gas hydrates. Model fits to electrolyte/gas hydrate experimental data were an improvement over previously published models. For example, average errors for four salt–CO 2⋅6H 2O systems were reduced from 7.2 ( ± 4.1 ) % to 3.0 ( ± 1.8 ) % . Similarly, average errors for 13 salt–CH 4⋅6H 2O systems were reduced from 4.3 ( ± 1.1 ) % to 3.0 ( ± 0.6 ) % . The results of this work demonstrate the critical importance of the electrolyte component in gas hydrate models.

Reductive cleavage of Se-Se bond by Sm/NiCl2 or Sm/NiCl2 6H2O system : A novel preparation of unsymmetrical aryl selenides

The Sm/NiCl 2 or Sm/NiCl 2 .6H 2 O system promoted diarylselenides to react with alkyl halides to afford unsymmetrical aryl selenides in good yields under mild and neutral conditions.

Comparative magnetic studies of (Sm, Nd) trichloroacetates and their heteronuclear CuLn2(CCl3COO)8·6H2O systems: structure and spectroscopy of a new type of Eu trichloroacetate

Two series of compounds: heteronuclear CuLn2(CCl3COO)8·6H2O (Ln = Nd and Sm) and their simple analogues Ln(CCl3COO)3·2H2O (Ln = Eu, Nd, Sm) were synthesized. New Eu(III) trichloroacetate; Eu(CCl3COO)3·3H2O·CH3OH was obtained, its molecular structure was determined by X-ray diffraction and compared with the data of respective systems reported earlier. Magnetization was measured and the susceptibility was derived in the limit of low field. Magnetic susceptibilities were calculated and discussed for series of homo- and hetero-nuclear chloroacetates.Untypical hysteresis was found (two loops) in samarium trichloroacetate. This phenomenon is most probably the effect of flops of spins in magnetic fields of 30,000Oe and very weak (if any) interaction intermediated by weak hydrogen bonding between the chains. A similar magnetic behavior was observed in neodymium carboxylate where the magnetic ordering was observed as a result of Nd–Nd interaction at low temperature (1.6K). For this system, the magnetic moment depends on magnitude of the magnetic field and ferromagnetic ordering appears at low temperatures. The strongest interactions of coupled ions and antiferromagnetic ordering with TN=6.5K were found in CuSm2(CCl3COO)8·6H2O single crystals.Heisenberg model was applied in the calculations for three interacting ions located linearly. The following relation was derived: χM=Ng2μβ2kT(12)+(12)exp(J2/kT)+5exp(J2/kT)−exp(1,5J1/kT)2+2exp(J2/kT)+4exp(J2/kT)−exp(1,5J1/kT) and applied in calculations of the exchange integrals. Mechanism of the exchange interaction was discussed on the basis of the obtained results.

Water adsorption and hydrolysis on molecular Al oxides and hydroxides—solvation versus cluster formationElectronic Supplementary Information available. See http://www.rsc.org/suppdata/cp/b1/b106318a/

Addition of water to the AlO(OH)(g) molecule and to the corresponding binuclear anhydride Al2O3(g) are studied by means of quantum chemistry. The AlO bond and the Al–O–Al bridge are found to be highly reactive towards water, and the final products are determined as Al(OH)3(g) and the dimer Al2(OH)6(g). The addition of further H2O molecules to Al(OH)3(g) was used to model micro-solvation. Two different types of cluster structures are found for Al(OH)3·nH2O. One type contains an Al(OH)4−/H3O+ ion-pair, for which the core anion displays a four-coordinated geometry on Al. The second type displays a six-coordinate Al, while tending to form a cationic core. Both structures require a Al(OH)3·6H2O(g) system as computational model to be observed. For neutral environments, polymerization of Al(OH)3 is preferred over the solvation of monomeric species. The results are understood to reflect the amphoteric dissolution chemistry of aluminium hydroxide under acidic or alkaline conditions.

ChemInform Abstract: A Novel Method for the Chemoselective Reduction of Azides to Amines with a Sm/CoCl2×6H2O System.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Cleavage of S-S Bond by Sm/cat. CoCl2 or Sm/cat. CoCl2 • 6H2O System: A Novel Method for the Synthesis of Thiolesters

The Sm/cat. CoCl2 or Sm/cat. &Cl2 • 6H2O system promoted disulfides to react with anhydrides or acyl chlorides to afford thiolesters in good yields under mild and neutral conditions.

Crystals field energy levels and transition line strengths of neodymium in trigonal Na 3[Nd(oxydiacetate) 3]·2NaClO 4·6H 2O

Locations and assignments of 119 crystal-field levels are reported for Nd 3+ in the trigonal Na 3[Nd(oxydiacetate) 3]·2NaClO 4·6H 2O levels span 34 of the 37 J-multiplet manifolds split out of the 4f 3 electronic configuration of Nd 3+ between 0 and 40000 cm −1, and they were located and assigned from axial and orthoaxial (σ- and π-polarized) absorption measurements performed on single crystals at temperatures between 4.2 and 300 K. The energy level data are analyzed in terms of a parameterized model Hamiltonian for the 4f 3 electronic configuration, assumed to be perturbed by a crystal field of trigonal dihedral (D 3) symmetry. Parametric fits of calculated to empirical energy level data yields rms deviations (between calculated and observed energies) of ≈ 14 cm −1 for 119 levels and ≈ 12 cm −1 for the subset of 71 levels that derive from multiplet manifolds with J ⩽ 9/2. The Hamiltonian parameter values obtained from these energy level analyses are reported and are compared with results obtained from similar analyses of Nd 3+ in other crystals and of other Ln 3+ ions in the Na 3[Ln(oxydiacetate) 3]. 2NaClO 4·6H 2O system. In addition to energy level locations and assignments, quantitatively determined line strengths are reportedfor 47 trans low-temperature π-polarized orthoaxial absorption spectra. All of these transitions originate in the ground crystal-field level of the 4I 9 2 (ground) multiplet, and each occurs via a predominantly electric-dipole mechanism.

Comparison of crystal field parameters for Ln(C 2H 5SO 4) 3·9H 2O and Na 3(Ln(C 4H 4O 5) 3)·2NaClO 4·6H 2O systems

Each lanthanide ion is coordinated to nine oxygen atoms in both Ln(C 2H 5SO 4) 3·9H 2O and Na 3(Ln(C 4H 4O 5) 3)·2NaClO 4·6H 2O systems (C 4H 4O 5 2−  oxydiacetate  ODA), and in each case the LnO 9 coordination polyhedra have a slightly distorted tricapped trigonal prism structure. In Ln(C 2H 5SO 4) 3·9H 2O, all of the coordinated oxygen atoms are donated by water molecules, whereas in the Ln(C 4H 4O 4) 3 3− systems, six of the oxygen atoms are donated by negatively charged carboxylate groups and three by neutral ether moieties. Commensurate crystal-field energy level analyses are reported for these two types of systems, and the crystal field parameters obtained from these analyses are compared and discussed within the context of the “superposition model” for lanthanide-ligand field interactions.